Eighteen replicates (9 barrows, 9 gilts) were used to estimate the dietary available phosphorus (AP) needs of a high lean strain of pigs during each of four stages of growth (9 to 37, 37 to 65, 65 to 92, and 92 to 119 kg body weight [BW]). Pigs were self-fed a basal diet supplemented with one of six incremental additions of AP from monodicalcium phosphate. Initially (9 to 37 kg), pigs were fed a .16% AP diet supplemented with 0, .08, .16, .24, .32, or .40% AP. After each 28 ± 3 kg of BW gain, the AP concentration of the basal diet as well as the incremental additions of AP were reduced to 80% of that fed during the previous growth stage.

Estimated dietary AP needs were similar between barrows and gilts. Daily dietary intakes of AP estimated to maximize body weight gain and gain/feed ratios were estimated as 3.15, 5.6, 4.95, and 4.95 g, respectively, for animals fed from 9 to 37, 37 to 65, 65 to 92, and 92 to 119 kg BW. These daily intakes were achieved with dietary concentrations of AP of .30, .26, .17, and .16%, respectively. Intakes of AP below the estimated needs resulted in negative biological and economical consequences.